Nodejs Application

app.js

@@ -0,0 +1,9 @@
+const fs = require("fs"); // require the fs module to manipulate with file system 
+const express = require("express"); // requiring the express module 
+const app = express();
+const morgan = require("morgan")
+app.use(morgan("dev")); // using a morgan middleware to get the requested url at the client side to print at the console
+app.use(express.json()); // using express.json() middleware to further read the body the code to handle post ,patch,put requests
+const userRouters = require("./userRoutes"); // Importing the packages rounters that routes the data acoording to the http methods
+app.use("/", userRouters); // whenver the home page is requested the control flow goes to the userRoute.js which routes according to the url
+module.exports = app; // exporting to be used by the server.js file which is the starting file

server.js

@@ -0,0 +1,8 @@
+/*This is starting file of the nodejs application */
+const app = require("./app"); // 
+const port = 3000;
+
+/*Starting server at port 3000 using the listen function*/
+app.listen(port, () => {
+    console.log("The server is started and listens at port 3000");
+});

userControllers.js

@@ -0,0 +1,109 @@
+const fs = require("fs"); // requiring the module to manipulate with file system 
+const userJSON = JSON.parse(fs.readFileSync(`${__dirname}/data/users.json`, { encoding: "utf-8" })); // reading the json which is sample data created by me which consist of user info
+const findObject = (getId) => {
+    for (let i = 0; i < userJSON.length ; i++) {
+        if (userJSON[i] != null && userJSON[i].id === getId) {
+            return userJSON[i];
+        }
+    }
+    return undefined
+}
+
+/*The url is get all the users names thus we applied a get request method send the entire json file with respective status*/ 
+exports.getAllUsers = (requestUsers, responseUsers) => {
+    responseUsers.status(200).json({
+        status: "OK",
+        data: {
+            userJSON
+        }
+    });
+}
+/*This url the client sends the data as json object and we write into the json file a post request*/
+exports.postUsers = (requestUsers, responUsers) => {
+    const newObject = requestUsers.body;
+    userJSON.push(newObject);
+    fs.writeFile(`${__dirname}/data/users.json`, JSON.stringify(userJSON), (err) => {
+        responUsers.status(201).json({
+            status: "Written successfully",
+            data: {
+                newObject
+            }
+        });
+    })
+}
+
+/*This url an id is mentioned additionally which should inturn fetch the particular user with the respective id */ 
+exports.getSpecificUser = (requestUser, responseUser) => {
+    const getId = Number(requestUser.params.id);
+    const getData = findObject(getId);
+    console.log(getData)
+    if (!getData) {
+        responseUser.status(404).json({
+            status: "Invalid Id",
+            message: "Data not found"
+        })
+    }
+    else {
+        responseUser.status(200).json({
+            status: "OK",
+            data: {
+                getData
+            }
+        });
+    }
+
+}
+
+/*A patch request is update a key for particular json object in the json file with respective to user ID*/
+exports.updateUser = (requestUsers, responseUsers) => {
+    const getId = Number(requestUsers.params.id);
+    const getObject = findObject(getId);
+    if (!getObject) {
+        responseUsers.status(404).json({
+            status: "Not found",
+            message : "Invalid data"
+        });
+    }
+    else {
+        const getId = Number(requestUsers.params.id);
+        const getCollege = requestUsers.body.college
+        console.log(getCollege);
+        userJSON[getId].college = getCollege;
+        fs.writeFile(`${__dirname}/data/users.json`, JSON.stringify(userJSON), (err) => {
+            responseUsers.status(201).json({
+                status: "Updated successfully",
+                data: {
+                    getObject
+                }
+            });
+        })
+    }
+}
+
+/*A delete request is used to delete a json object with according to the user Id specified in the url params*/
+exports.deleteUser = (requestUser, responseUser) => {
+    const getId = Number(requestUser.params.id);
+    const getObject = findObject(getId);
+    console.log(getObject)
+    if (!getObject) {
+        responseUser.status(404).json({
+            status: "Not found",
+            message : "Invalid data"
+        });
+    }
+    else {
+        const getObject = userJSON.find(data => {
+            if(data != null)
+                data.id === getId
+        })
+        delete userJSON[getId];
+        fs.writeFile(`${__dirname}/data/users.json`, JSON.stringify(userJSON), (err) => {
+            responseUser.status(204).json({
+                status: "Deleted successfully",
+                data: {
+                    getObject
+                }
+            });
+        })
+    }
+}

userRoutes.js

@@ -0,0 +1,14 @@
+const express = require("express");
+const userApp = express.Router(); // mounting a rounter to handle the http request accordingly 
+const userController = require("./userControllers"); //The application logic to handle the http request stored in userController.js file following the MVC model
+
+userApp
+    .route("/api/users")
+    .get(userController.getAllUsers)
+    .post(userController.postUsers);
+userApp
+    .route("/api/users/:id")
+    .get(userController.getSpecificUser)
+    .patch(userController.updateUser)
+    .delete(userController.deleteUser);
+module.exports = userApp;

users.json

@@ -0,0 +1 @@
+[null,{"id":1,"firstName":"ghi","lastName":"jkl","cgpa":9.5,"college":"Guidy College of Engineering","SSLC":95,"HSC":94},{"id":2,"firstName":"mno","lastName":"pqr","cgpa":8.8,"college":"IIIT ,Delhi","SSLC":89,"HSC":98},{"id":3,"firstName":"stu","lastName":"vw","cgpa":8.2,"college":"Indian Institute of Technology","SSLC":100,"HSC":96},{"id":4,"firstName":"yz","lastName":"abc","cgpa":9.2,"college":"National Institute of Technology","SSLC":90,"HSC":92},{"id":0,"firstName":"abcdef","lastName":"1234","cgpa":9,"college":"Indian Institute of Information Technology","SSLC":99,"HSC":99},{"id":0,"firstName":"abcdef","lastName":"1234","cgpa":9,"college":"Indian Institute of Information Technology","SSLC":99,"HSC":99}]